EEG, Alpha Waves and Coherence

EEG, Alpha Waves and Coherence

Date: May 2010
Creator: Ascolani, Gianluca
Description: This thesis addresses some theoretical issues generated by the results of recent analysis of EEG time series proving the brain dynamics are driven by abrupt changes making them depart from the ordinary Poisson condition. These changes are renewal, unpredictable and non-ergodic. We refer to them as crucial events. How is it possible that this form of randomness be compatible with the generation of waves, for instance alpha waves, whose observation seems to suggest the opposite view the brain is characterized by surprisingly extended coherence? To shed light into this apparently irretrievable contradiction we propose a model based on a generalized form of Langevin equation under the influence of a periodic stimulus. We assume that there exist two different forms of time, a subjective form compatible with Poisson statistical physical and an objective form that is accessible to experimental observation. The transition from the former to the latter form is determined by the brain dynamics interpreted as emerging from the cooperative interaction among many units that, in the absence of cooperation would generate Poisson fluctuations. We call natural time the brain internal time and we make the assumption that in the natural time representation the time evolution of the EEG variable ...
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Changes in quantitative EEG and low resolution tomography following cranial electrotherapy stimulation.

Changes in quantitative EEG and low resolution tomography following cranial electrotherapy stimulation.

Date: August 2006
Creator: Kennerly, Richard C.
Description: The effects of cranial electrotherapy stimulation (CES) on human EEG and brain current density were evaluated by quantitative electroencephalography (qEEG) and low resolution brain electromagnetic tomography (LORETA). A total of 72 research subjects were provided with a single session of CES, 38 were provided with 0.5 Hz CES while 34 were provided with 100 Hz CES. The qEEG paired t-tests revealed that in both frequencies of CES there was a significant (.05) increase in alpha relative power with concomitant decreases in delta and beta relative power. The 0.5 Hz CES decreased a wider frequency range of delta activity, while the 100 Hz CES decreased a wider frequency range of beta activity; suggesting some difference may exist in the EEG response to different frequencies of CES. The changes found in qEEG relative power were consistent with the affective and cognitive effects of CES reported in the literature, such as increased relaxation and decreased anxiety. Statistically significant changes for qEEG values other than relative power, such as coherence, amplitude asymmetry, phase lag and power ratios were also found. The LORETA paired t-tests found statistically significant (.05) increases in cortical and subcortical theta and alpha frequency current density with concomitant decreases in delta ...
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QEEG and LORETA findings in children with histories of relational trauma.

QEEG and LORETA findings in children with histories of relational trauma.

Date: May 2010
Creator: Bigby, Janice A.
Description: Abuse and neglect occurring in childhood have been associated with a number of functional and physiological effects on the brain. This study extends previous research that investigated the quantitative electroencephalogram (qEEG) patterns in children with histories of relational trauma through the inclusion of additional participants and measures. As in previous studies, the relative power, absolute power, and coherence values in children with histories of abuse were compared to the Neuroguide database. Results did not show any significant differences in relative or absolute power in the theta range. Similarly, there were no significant coherence differences. Database comparisons were also made using low resolution electromagnetic tomography (LORETA) in order to determine which sub-cortical brain structures may be affected by abuse or trauma, though there were no significant differences in any frequency (0-30Hz). A review of the literature suggests that the prevalence of mu in normal adults and children ranges from 0 to 19%. The present study found a mu prevalence rate of 60.6% in the children who experienced abuse or neglect. Finally, comparisons were made between participants who demonstrate a mu pattern and those who do not to determine if this pattern is associated with certain behavioral and/or attention problems as assessed ...
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Anxiety, Depression, and Sleep Disorders: Their Relationship and Reduction with Neurotherapy

Anxiety, Depression, and Sleep Disorders: Their Relationship and Reduction with Neurotherapy

Date: August 2010
Creator: Fisher, Christopher, Alan
Description: This study investigated the relationship among anxiety, depression, and sleep disturbances and the treatment of these three disorders through neurotherapy. Research suggests that these conditions commonly co-occur in the general population and that central nervous system (CNS) arousal may play a primary role in the development and maintenance of these disorders. Several recent studies suggested that neurotherapy, a biofeedback-based treatment for CNS dysregulation, might be an effective treatment for comorbid conditions, particularly the ones of interest here, depression, anxiety, and sleep disturbances. This investigation used a clinical case-series design to assess pre/post neurotherapy changes on objective measures of anxiety, depression, and sleep and to determine whether changes in anxiety and depression then predict improvements in sleep quality. Data for 23 participants (10 males) were obtained from files of adults (Mage = 40.22 years, SD = 16.20) who received at least 15 neurotherapy sessions (M = 47.83 sessions, SD = 22.23) the University of North Texas Neurotherapy Lab. Matched pair t-tests revealed that symptoms of sleep disturbance, depression, and anxiety showed significant improvements following neurotherapy. Neurotherapy treatment effect sizes generally ranged from moderate to large (d = .414 - .849). Multiple regression analysis found that changes in self-reported anxiety symptoms, but ...
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Neuropsychologic correlates of a normal EEG variant: The mu rhythm.

Neuropsychologic correlates of a normal EEG variant: The mu rhythm.

Date: August 2008
Creator: Simms, Lori A.
Description: Although the mu rhythm is traditionally defined as a normal EEG variant, recent evidence suggests that mu may have functional significance in a variety of disorders such as autism, Parkinson's disease, and multiple sclerosis. While an increasing number of articles have focused on the blocking mechanism of mu in relation to various cognitive processes and disorders, few have examined the significance of a prominent mu rhythm in the background EEG. A few studies have examined the relationship between the mu rhythm and psychological disturbance, such as attentional and affective disorders. Increasing evidence suggests that EEG and qEEG variables may be useful in classifying psychiatric disorders, presenting a neurophysiological alternative to traditional symptom-based diagnosis and classification. Thus, the intention of the present study was to examine the relationship between neuropsychological variables, gathered from multiple assessment sources, and the presence of a prominent mu rhythm in the EEG. Results did not show a statistically significant difference between individuals with and without a prominent mu rhythm on the Test of Variables of Attention (TOVA); although individuals in the mu group showed a pattern of increased impulsivity and performance decrement over time. For adults, no significant differences were observed between groups on psychological variables ...
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The effects of sequential versus referential montage neurofeedback amplitude training on QEEG measures of phase and coherence.

The effects of sequential versus referential montage neurofeedback amplitude training on QEEG measures of phase and coherence.

Date: August 2008
Creator: Ramezani, Amir
Description: An important clinical research question to be answered in the field of neurofeedback (NF) is whether amplitude training affects connectivity between cortical sites. This study hypothesizes that, following NF amplitude training, there will be a difference in QEEG coherence and phase measures between NF training done using referential montages and using sequential montages. The study examined case files of 16 adult clients from the University of North Texas Neurotherapy Lab who had received NF training that consisted of either referential or sequential placement amplitude training (no coherence training) and who received both pre- and post- treatment QEEGs. Sixty-eight percent of the cases consisted of referential placements, while 34% of the cases consisted of sequential placements. All frontal site phase and coherence abnormal z-scores at pre-treatment were converted to deviation scores and compared by general linear model analysis of variance to post-treatment deviation scores. Effect size r-values and eta square values indicate that differences between referential and sequential electrode placements after NF amplitude training are moderately high. This study shows that referential placements tend to increase phase scores and decrease coherence scores, while sequential placements tend to decrease phase scores and increase coherence scores.
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The Effects Of The Allocation Of Attention Congruent With Lateralized Cognitive Tasks On EEG Coherence Measurements

The Effects Of The Allocation Of Attention Congruent With Lateralized Cognitive Tasks On EEG Coherence Measurements

Date: May 2002
Creator: Hill, Cynthia DeLeon
Description: The single task condition of the Urbanczyk and Kennelly (1991) study was conducted while recording a continuous electroencephalographic (EEG) record. Attention was allocated by instructed lateral head orienting and eye gaze either congruently or incongruently with lateralized cognitive tasks. Thirty university subjects retained a digit span or a spatial location span for a 20 second retention interval. EEG data were extracted from the 20 second retention intervals and interhemispheric coherence was calculated for homologous sites in the temporal, parietal and occipital regions of the brain. There was a main effect for group, with congruent orienting producing greater coherence values than incongruent orienting. This effect of attention on alpha coherence values was found in the low alpha (8-10 Hz) frequency band. This provides evidence that the lower alpha frequency band is reflective of manipulations of attention. The higher coherence measures for the congruent orienting group indicates that homologous regions of the two hemispheres are more coupled into a single system when lateralized attention activates the same hemisphere performing the cognitive task. In the higher alpha frequency band (11-13 Hz) group, sex, site and task interacted. This provides evidence that the higher alpha band is more affected by cognitive processing of the ...
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